Aerosol measurements may be used e.g. for checking whether the mass concentration of aerosol particles in the exhaust gas of an internal combustion engine is lower than a predetermined limit. The mass concentration of aerosol particles may be measured e.g. by collecting the aerosol particles by a filter, and by weighing the filter in order to determine the total mass of the collected particles. After weighing, the average particle mass concentration may be calculated by dividing the total mass of the collected particles by the total volume of the gas guided through the filter. Collecting a sufficient amount of aerosol particles by the filter may require a relatively long time period, e.g. several hours. Weighing the filter may require manual work, or may require the use of expensive automatic weighing equipment.